Heat sink



FIG. 1 is a top perspective view of the new design for a heat sink as seen from the front, top;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a right side elevational view thereof, the opposite side view being a mirror image thereof; and,

FIG. 7 is a bottom perspective view thereof.

The broken lines shown in the drawings illustrate unclaimed portions of the heat sink and form no part of the claimed design. 

CLAIM The ornamental design for a heat sink, as shown and described. 